This invention relates to a pressure sensor, and more particularly to a pressure sensing unit for such a sensor using a magnetostriction effect to change inductance in response to pressure.
Conventionally, a fluid or gas pressure is measured by use of a diaphragm provided with a strain gauge having a piezo-resistance effect. A pressure sensor of such construction is designed with a bridge connection for the purpose of improving the sensitivity because the sensor, when used as a strain gauge unit, undergoes small changes in resistance with respect to the amount of strain. However, a sufficient output is not obtainable from the sensor and its handling is very troublesome. On the other hand, a semiconductor sensor using a silicon plate as the diaphragm which is provided with a strain gauge has recently been proposed as a sensor having a relatively large output. Such a silicon semiconductor sensor, however, is deficient in that its output depends very largely on the temperature and requires a temperature compensating circuit and moreover the silicon plate diaphragm is relatively fragile when subjected to an excessive pressure.